1. Field of the Invention
This invention relates to a valve for use with hydraulic ram assemblies and in particular to a valve for use in inhibition of fluid bypass through the piston especially when a plurality of hydraulic ram assemblies are connected in series.
When a plurality of hydraulic ram assemblies are connected in series with a conduit interconnecting an outlet port of a respective hydraulic ram assembly to an inlet port of an adjacent hydraulic ram assembly effective operation of the plurality of hydraulic ram assemblies can be adversely effected if bypass of hydraulic fluid occurs past the piston seals or for any other reason bypass or leakage of fluid may occur between the pressure side of the piston and the non-pressure side. This means that the relative positions of the respective pistons in each hydraulic cylinder can alter and thus proper and effective sequencing of fluid flow between adjoining pistons is impaired.
2. Description of the Prior Art
Fluid leakage or bypass through the piston may occur through mechanical reasons, seal faults, or excess pressure being applied.
Various attempts have been made to solve this particular problem and they have included the provisions of grooves in the internal surface of the hydraulic cylinder wherein fluid may pass through or pass the piston connecting both sides during piston movement. There has also been the provision of check valves located in the piston or piston rod which are operated by spring loading or which alternatively are pushrod actuated but such check valves may only open in a direction opposing pressure thus allowing an interchange of fluid between the non-pressure side and the pressure side of the piston. However the major problem with these remedies was that fluid bypass still had a tendency to occur when the piston changed direction after reaching one end of the hydraulic cylinder from either a shock loading, or through an intentionally high operational loading or until the pushrod has ceased to contact the end of the hydraulic cylinder. Thus under these conditions the sudden or abrupt change in direction of the piston in the cylinder was responsible for reverse flow or bypass of fluid to occur from the non-pressure side of the piston to the pressure side before and/or after impact or contact with the pushrod and cylinder end.
In the case of a check valve or spring loaded ball valve under high load conditions, often the ball was separated from its accommodating seat before and/or after impact and thus fluid leakage could occur.
It also had to be borne in mind in regard to the check valves described above that they were ineffective in preventing fluid bypass through the piston or piston rod from the pressure side to the non-pressure side.
It is therefore an object of the invention to provide a valve for use in hydraulic ram assemblies capable of alleviating fluid leakage or bypass through the piston and thus minimizing the problems associated with the prior art.